The invention relates to a method and device for centering a wheel with the features recited in the preamble of claims 1 and 3.
It is known to compensate the lateral runout and radial runout of a wheel with a device operating as a centering aid. The wheel to be tested it is hereby clamped in a mount of the centering aid and rotated. The values of the axial and radial runout of the wheel rim are measured by suitable measuring devices. The lateral runout and the radial runout are then compensated by rotating the spoke nipples of the wheel. Dial gauges are customarily used as measuring devices. Dial gauges disadvantageously only indicate the instantaneous value of the lateral and radial runout, so that several revolutions of the wheel are required if the lateral and radial runout is to be accurately corrected from a determination of the maximum deviations. On the other hand, the pointers of the dial gauges which typically have displays accurate to about 0.01 mm may require several revolutions when measuring the axial and radial deviations of the wheel rim. As a result, the number of revolutions of pointer of the dial gauge typically have to be counted for determining the measurement values. The entire process for determining the measurement values is therefore time-consuming, and the person performing the test has to be attentive and concentrate, since he/she has to always remember the number of revolutions. Finally, this process can easily lead to errors in the determination of the measurement values, which makes it more difficult and more time-consuming to correct the deviations in the axial and radial direction.
It is therefore an object of the invention to provide a method and device of the aforedescribed type which enables centering of a wheel in a simple, quick and accurate matter.
The object is solved by a method and a device with the characterizing features recited in the independent claims 1 and 3. According to the method, the wheel hub is clamped in a wheel mount of a centering stand, the wheel is rotated, whereby each of the maximum left and right lateral runout of the wheel rim is determined as a measurement value from a complete revolution of the wheel, the measurement value of the left (respectively right) maximum lateral runout of the wheel rim is recorded, including its mathematical sign, a negative sign is associated with the measurement value left of the zero position and a positive sign is associated with the measurement value right of the zero position, the wheel is clamped after being rotated by 180xc2x0, each of the maximum left and right lateral runout of the wheel rim is determined as a measurement value from a complete rotation of the wheel, the first left (respectively the first right) maximum lateral runout and the second right (respectively the second left) maximum lateral runout of the wheel rim are subtracted from each other, the value determined in the previous step is divided by 2, with a positive sign associated with the so obtained value, the value determined in the previous step is subtracted from the right (respectively left) maximum lateral runout of the wheel rim, the wheel is rotated until the center pointer of the pointer mechanism points to the value determined in the previous step, the adjusting wheel of the pointer mechanism is rotated, until the center pointer points to zero, the maximum left and right lateral runout of the wheel rim is indicated by the two maximum pointers of the pointer mechanism after a complete revolution of the wheel, the wheel is rotated, until the center pointer of the pointer mechanism reaches one of the two maximum pointers which indicates the maximum left (respectively right) lateral runout of the wheel rim, the lateral runout of the wheel rim is corrected in a conventional manner by turning to the spoke nipples, whereby the spoke indicated by the pointer mechanism is tensioned or loosened via the spoke nipple, and the spokes are tensioned or loosened, starting in the region of the maximum left and right lateral runout of the wheel rim, sequentially in an alternating order and in at least two steps, with a corresponding number of revolutions of the wheel, until the left and right lateral runout remains within a minimum range.
According to a preferred embodiment of the invention, the maximum inward and outward radial runout of the wheel rim is subsequently determined from a full revolution of the wheel as a measurement value representing a deviation from a circle, the zero of the pointer mechanism is set between these measurement values, the radial runout of the wheel rim is corrected in a conventional manner by turning the spoke nipples, whereby the spoke indicated by the pointer mechanism is tensioned or loosened via the spoke nipple, the spokes are tensioned or loosened, starting in the region of the maximum radial runout of the wheel rim, sequentially inwardly and outwardly in an alternating order and in at least two steps, with a corresponding number of revolutions of the wheel, until the inward and outward radial runout is within a minimum range, and during the correction of the radial runout, the lateral runout of the wheel rim is monitored and optionally corrected.
According to the invention, the center position of the wheel rim is determined by subtracting the first left (respectively right) maximum lateral runout from the second right (respectively left) maximum runout, the value determined in the previous step is divided by two, thereby obtaining the distance of the second right (respectively left) maximum lateral runout from the center of the wheel axis, including the mathematical sign. The wheel is then rotated until the center pointer indicates the second right (respectively left) maximum lateral runout. The adjusting wheel of the pointer mechanism is then turned until of the center pointer points to the value determined in the previous step. The other steps are performed as described above. With this method, the center position of the wheel rim can be determined in all situations, even if the dial gauge is initially set to an arbitrary value.
According to another alternative feature for eliminating the lateral runout, the wheel can be rotated until the center pointer reaches the maximum value from the left and right maximum lateral runoutxe2x80x94corresponding to the absolute maximum lateral runout. The spoke nipple at this location is turned until the center pointer indicates approximately half the absolute maximum lateral runout. During the following wheel revolution, another absolute maximum lateral runout is determined which, however, has a smaller value than the previously corrected maximum lateral runout. This process is repeated until the lateral runout is decreased to a desired value.
The radial runout can be eliminated in an analogous manner by rotating the wheel until the center pointer reaches the absolute maximum radial runout. The spoke nipple at this location is turned until the center pointer indicates approximately half of the absolute maximum radial runout. The adjacent spoke nipple is turned until of the radial runout produced by the previous adjustment of the spoke nipple is minimized. The next absolute maximum radial runout is then determined by again rotating the wheel, which however has a smaller value that the previously determined radial runout. This process is repeated a number of times until the absolute maximum radial runout is decreased to a desired value.
The device according to the invention includes as measurement devices at least one, preferably two pointer mechanisms of identical construction which preferably are releasably secured on the centering stand, wherein one pointer mechanism measures the lateral runout and another pointer mechanism measures the radial runout of the wheel rim, with an axially displaceable feeler rod being supported in each of the two pointer mechanisms, wherein the feeler rod is operatively connected with a support frame that can pivot about a pivot axis so that the axial displacement motion of the feeler rod is transformed without play into a pivoting motion of a center pointer, wherein the center pointer is operatively connected to both a left maximum pointer and a right maximum pointer, with the maximum pointers being configured to separately indicate the maximum left and right lateral runout of the wheel rim (10) when the lateral runout of the wheel rim (10) is tested and the maximum inward and outward runout of the wheel rim (10) when the radial runout of the wheel rim (10) is tested, and wherein the center pointer is affixed on the support frame that can pivot about the pivot axis, and wherein two mutually parallel, spaced-apart guides are arranged in the support frame that guide a ball-shaped transmission element on both sides. This arrangement allows the wheel to be centered quickly, accurately and in a simple matter. The method for intentionally and accurately centering the wheel is based on an exact determination of the center position and desired plane of the wheel. During the centering operation, the wheel rim can be exactly matched to the desired plane in individual steps. The pointer mechanism according to the invention provides an amplified display of the lateral and radial runout values of the wheel. The pointer mechanism of the invention indicates the runout of the wheel in a large and easily visualizable display area within a pointer range of less than 180xc2x0. The maximum pointers can display and measure the maximum deflection of the center pointer both to the left and to the right. Advantageously, when centering the wheel, one can start from the regions of maximum runout of the wheel rim and align these regions intentionally with the desired plane.
According to a preferred embodiment of the invention, a clamping fixture for receiving a wheel hub can be configured so as to be self-adjusting, so that the wheel to be adjusted can advantageously assume an exactly reproducible position. This is necessary so that the wheel always has a uniquely determined, defined center position during the centering processxe2x80x94even after the wheel is rotated according to the invention. This is easily achieved by the self-adjusting design. In particular, the wheel can be exactly positioned with a clamping fixture that has two mutually parallel, spaced-apart retaining elements which each include a receiving groove, which preferably form a 2-point-support for the hub. The 2-point-support guarantees a reproducibly defined position of the hub and hence also of the wheel.
According to another advantageous embodiment of the invention, each of the retaining elements can include a locking element which preferably can be latched. In this way, a hub of a wheel inserted into the receiving groove of the retaining elements can be held by the locking element in its initial position, whereby the initially assumed position is also maintained during the use of the centering device. The locking element preferably forms a 1-point-support for a hub, so that the entire hub is supported by a 3-point-support. The hub and hence also the wheel can then be precisely positioned.
Additional advantageous embodiments of the invention are described in the additional features recited in the dependent claims.